Method of cleaning plate-type filter elements located in a tank filter

ABSTRACT

In cleaning plate-type filter elements in a tank filter, the tank is opened and a cleaning tube is placed upwardly around one of the downwardly extending filter elements providing an annular flow space along the length of the element. A seal member is located in the upper end of the cleaning tube to close off the upper end of the annular flow space. Pressurized cleaning fluid is supplied into the lower end of the tube where it flows upwardly through the annular space and then into the filter element to dislodge any contamination. The material displaced continues its flow through the filter element in the same direction as is taken by the fluid being filtered.

This is a division of application Ser. No. 963,752 filed Nov. 27, 1978now U.S. Pat. No. 4,201,674.

SUMMARY OF THE INVENTION

The invention is directed to a method of cleaning plate-type filterelements located within a tank filter.

Cleaning of tank filters after a daily filtration operation isparticularly important, since the filters are generally not opened for alonger period of time. Only a safe method which adequately cleans thefilters so that a satisfactory deposition is obtained on a daily basisguarantees excellent filtration quality. Nevertheless, due to improperhandling, over a period of time, a certain contamination of themicrofine slots of individual plate-type filter elements may occurresulting in the obstruction of flow and in a non-uniform deposition.

After daily usage at the latest, it is necessary to disassemble theindividual filter elements made up of a plurality of discs stacked oneon top of the other and forming the microfine slots when the discs arepressed together. Due to the large number of filter elements in a tankfilter, this cleaning procedure is both time-consuming and cumbersome.

Therefore, the primary object of the present invention is to provide amethod of cleaning plate-type filter elements within a tank filter wherethe filter elements or sections of the elements in the assembled statecan be freed of any difficult-to-remove residues by flowing apressurized fluid from the exterior into the elements in the directionof the filtration path.

In accordance with the present invention, the plate-type filter elementsare cleaned in the assembled state from the outside toward the inside inthe direction of the flow of the filtrate. To carry out the cleaningoperation, the bottom of the chamber for the unfiltered liquid is openedand a cleaning tube is guided either for a partial or total axial lengthof the filter element from the bottom toward the top so that thecleaning tube forms, in combination with the filter elements, a chamberinto which the pressurized cleaning fluid is introduced through aconnection at the lower end of the cleaning tube. The cleaning fluidflows into an annular gap or space between the inside surface of thecleaning tube and the outside of the plate-type filter elements.

Further, the apparatus used in carrying out the method of the presentinvention includes a tank filter divided by a horizontally arrangedsheet into an upper filtrate chamber and a lower chamber for theunfiltered liquid with the filter elements projecting downwardly fromthe sheet into the lower chamber. The tank filter is distinguished overwhat has been done in the past by the fact that the lower chamber can beopened and a cleaning tube which has a locking device and/or a sealingelement on its upper end can be placed over and in interconnection withthe filter element. At its lower end, the cleaning tube has a connectionthrough which the cleaning agent or fluid is introduced for flowupwardly through the cleaning tube and then inwardly into the filterelement.

In one embodiment, it has been found advantageous to secure the lockingelements on the cleaning tube into a groove on the filter element.

In another embodiment of the present invention, the cleaning tube isscrewed onto the filter element.

In still another embodiment it has proven to be especially advantageousthat the locking and/or sealing elements can be secured to the filterelement by the pressure developed within the cleaning tube by thecleaning fluid so that practically any section of the filter element canbe cleaned.

The various features of novelty which characterize the invention arepointed out with particularity in the claims annexed to and forming apart of this disclosure. For a better understanding of the invention,its operating advantages and specific objects attained by its use,reference should be had to the accompanying drawings and descriptivematter in which there are illustrated and described preferredembodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

FIG. 1 is a schematic sectional view through a tank filter illustratingthe present invention;

FIG. 2 is an axially extending cross-sectional view of one embodiment ofa cleaning tube usable in cleaning the tank filter of FIG. 1; and

FIGS. 3 to 5 show three other embodiments of a cleaning tube arranged tobe sealed to a filter element.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 a tank filter is shown divided into an upper hood-shapedfiltrate chamber 1 and lower unfiltered liquid chamber 2 by a generallyhorizontally arranged intermediate sheet 3. Lower chamber 2 consists ofan upper cylindrically shaped portion and a lower conically shapedportion 2' with the downwardly extending surfaces of the lower portion2' converging inwardly in the downward direction. Intermediate sheet 3dividing the tank filter into the two separate chambers 1,2-2', has anumber of bores in which back-washable filter elements extend downwardlythrough the sheet from the upper chamber 1 into the upper portion of thelower chamber 2-2'. At its lower end, the lower portion 2' of the lowerchamber has a connecting piece with a distributor ring connected to asupply line 5 for introducing unfiltered liquid. Outlet lines 6 for thefiltrate are connected to the upper portion of the upper chamber 1.

In carrying out the cleaning operation, the lower portion 2' of theunfiltered liquid chamber 2 can be displaced laterally so that theindividual filter elements 4 are accessible at their lower ends. Thesefilter elements 4 have threaded bushings at their upper ends whichproject through the intermediate sheet 3 into the lower chamber 2. Thebushings at the upper ends have a thread and/or a circumferential groovesuitable for connecting a cleaning tube 7 to the filter element 4. Notein FIG. 2 the upper end of the cleaning tube 7 has an internal thread 8while in FIG. 3 the upper end of the tube has locking elements 9 whichcan be pressed mechanically or through the application of pressure intoa corresponding groove in the filter element. At their lower ends, thecleaning tubes are provided with a hose connection 10 for introducing acleaning agent or fluid into the tube.

In carrying out the cleaning operation with the filter elements 4 in theassembled state, the lower portion 2' of the lower chamber 2 isdisplaced laterally and a cleaning tube 7 is placed over one of thefilter elements 4 sliding it upwardly from the bottom of the elementand, if appropriate, the cleaning tube is locked in place about theplate-type filter element. After the cleaning tube 7 has been securelymounted about the filter element 4, the cleaning fluid is suppliedthrough the hose connection 10 at the lower end of the tube at anincreased pressure, for example, 4 atmospheres absolute. The cleaningfluid flows in the direction of filtrate flow upwardly in the annularspace between the tube and the filter element passing through themicrofine slots between the individual discs of the filter element sothat even stubborn contamination is removed and washed out in thedirection of filtrate flow into the upper chamber 1. By laterallyenclosing the filter element 4 with the cleaning tube 7 during thecleaning operation, it is unnecessary to disassemble the individualfilter elements 4 or to provide any manual cleaning of the individualfilter discs.

As can be seen in FIG. 1, one cleaning tube 7 extends for the axiallength of the filter element it encloses up to the underside of theintermediate sheet 3. Another cleaning tube 7 is shown extending for ashort distance upwardly about another one of the filter elements 4. InFIGS. 4 and 5 cleaning tubes are shown for use in partial cleaning ofthe individual filter elements 4 or for cleaning contaminated sectionsof the elements. Adjacent their upper ends, the cleaning tubes shown inFIGS. 4 and 5 have sealing elements which provide a tight sealingcontact with the filter elements 4. In particular, the elasticallydeformable sealing element shown in FIG. 5 is pressed against thesurface of the filter element when pressure is applied within theinterior of the cleaning tube, that is, in the space between the tubeand the filter element. With this sealing element, the surface qualityof the outside surface of the filter element is of secondary importance.By using cleaning tubes constructed in this manner, a partial section orthe full length of a filter element can be satisfactorily cleaned.Cleaning individual sections of the filter elements is particularlypreferred. Cleaning a portion or the full axial length of a filterelement 4 is indicated by the two separate cleaning tubes shown in FIG.1.

What is claimed is:
 1. Method of cleaning plate-type filter elements ina tank filter where the tank filter comprises an upper chamber forfiltrate, a lower chamber for unfiltered liquid, a sheet separating theupper chamber from the lower chamber and a plurality of plate-typefilter elements depending downwardly from the upper chamber through thesheet into the lower chamber with the filter elements made up of aplurality of discs stacked one on top of the other and forming microfineslots therebetween when the discs are pressed together, wherein themethod comprises the steps of placing a tubular member around andlaterally enclosing at least an axially extending portion of aplate-type element from the end of the element spaced downwardly fromthe sheet and forming an annular chamber about the exterior of theelement with the inner surface of the annular chamber being defined bythe exterior surface of the plate-type element and the outer surfacebeing defined by the inner surface of the tubular member, sealing theupper end of the annular chamber between the exterior surface of thefilter element and the laterally enclosing tubular member, andintroducing a pressurized cleaning fluid directly into the lower end ofthe annular chamber for providing a body of the pressurized cleaningfluid in the annular chamber for flow directly inwardly from the annularchamber over the full annular and axial extent of the element within thelaterally enclosed chamber so that the full pressure of the pressurizedcleaning fluid within the annular chamber acts over the entire surfaceof the laterally enclosed portion of the element with the pressurizedcleaning fluid flowing inwardly between the plates of the filter elementin the same direction as normal filtering flow for dislodging anycontamination between the plates.
 2. Method, as set forth in claim 1,including the step of maintaining the cleaning fluid supplied into theannular chamber at a pressure of four atmospheres absolute.